Wino,
The other B757 accident around the same time wasat Cali which was a result of the crew selecting an incorrect navaid ("R" NDB) and they had a CFIT accident.
Both of these accident were listed as CFIT accidents.
40 seconds prior to impact of the Aeroperu B757, Lima ATC confirmed to the crew that they were receiving an transponder altitude readout of 9700 feet, whilst at the same time the GPWS was giving a "Too Low Terrain" warning (altitude information from RADALT).
Investigators concluded that all ports were covered up for the aircraft wash prior to flight.
It is clear that this represents a common failure mode of all three pitot-static systems: the backups suffer the same failure as the primary systems. It should also be clear that this failure mode is not computer-related: neither the design nor the operation of the LADC or RADC or any other computer contributed to this particular way of failing to deliver reliable air data.
The crew kept the aircraft airborne for 29 minutes without the aid of an altimiter, airspeed indicator or the air data computers.
This is a photo of part of the wreckage recovered showing the tape over the static ports.
